This invention relates to motors in general and more particularly to an improved cold start system particularly useful with gyroscope motors.
In gyro stabilized platforms for inertial guidance, it is common practice to start motors at cold temperatures (0.degree. C) in a very short time (2 seconds). Such is necessitated by the requirement for rapid reaction alignment in gyrocompassing within a few minutes in fighter type aircraft.
Another requirement placed on such apparatus is that the bearings in the motors must have long bearing life. This has dictated higher viscosities in the lubricating oil for the bearings which has in turn aggravated the problem of cold starting since oils of this nature get even more viscous at low temperatures.
The traditional solution in the prior art is to program the power supply during the start up cycle to supply a high voltage in order to bring the motors up to saturation and up to maximum torque. This means that the power supply must be designed for a maximum total power during the starting period which is much higher than the normal running power. Similarly, the switching module which converts the DC into AC to drive the motor must also be designed for higher voltage.
Thus, although the present solution works, it is obtained only through a higher cost in both the materials used and in increased weight of the apparatus. Thus, the need for an improved cold starting system which keeps the power supply and switching module requirements to a minimum, i.e. that required for normal running, but still provides fast starting at cold temperatures becomes evident.